ID 36
Type H - High priority request
Target 92-U-238
Reaction (n,g)
Quantity SIG - Cross section
Incident energy 20 eV - 25 keV
Accuracy 1-5 %
Field(s) Fission
Subfield Fast and Thermal Reactors
Accepted date 15-Sep-2008
Status Archived
Latest review date 16-May-2018



Project (context)

CEA Cadarache


Design phases of selected reactor and fuel cycle concepts require improved data and methods in order to reduce margins for both economical and safety reasons. A first indicative nuclear data target accuracy assessment was made within WPEC Subgroup 26 (SG-26). The assessment indicated a list of nuclear data priorities for each of the systems considered (ABTR, SFR, EPR, GFR, LFR, ADMAB, VHTR, EPR). These nuclear data priorities should all be addressed to meet target accuracy requirements for the integral parameters characterizing those systems (see the accompanying requests originating from SG-26).


Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties. The weighting factor λ is explained in detail in the accompanying document. Changes from the reference value of λ=1 show the the possible allowance for other target uncertainties. Two cases (A and B) are distinguished for λ≠1 (see Table 24 of the report).

Energy Range Initial versus target uncertainties (%)
    λ=1 λ≠1,a λ≠1,b λ=1 λ≠1,a λ≠1,b λ=1 λ≠1,a λ=1 λ≠1,a λ=1 λ≠1,a λ=1 λ≠1,a λ=1 λ≠1,a
9.12 - 24.8 keV 9 3 2 2 4 3 3 3 2 2 1 2 2     5 4
2.03 - 9.12 keV 3                 1 1            
22.6 - 454 eV 2                         1 1 1 1


Justification document

1. OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
2. OECD/NEA WPEC Subgroup 7 (SG-7) Final Report: "Nuclear data standards" (link to WPEC Subgroup 7 Report in PDF format, 450kb).

Comment from requester

Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.

Review comment

In this particular case high accuracy is required throughout the energy range. Only the groups shown above have initial uncertainties larger than the target uncertainties. The low initial uncertainty is a result of the standards evaluation (see SG-7 report above). Concerns have been raised that despite the excellent efforts of this subgroup an independent check is in order to verify the present view on required corrections to experimental work for the unresolved resonance range.

Entry status

Completed (as of SG-C review of May 2018) - New time-of-flight measurements have been performed worldwide, e.g., at LANSCE [Ullmann:2014], JRC-Geel [Kim:2016] and n_TOF [Mingrone:2017;Wright:2017]. These experimental data have been used in the CIELO evaluation [Sirakov:2017,Capote:2018] and for the evaluation of the standards [Carlson:2018]. The CIELO evaluated data have been adopted in ENDF/B-VIII.0 and JEFF-3.3; the evaluated uncertainties match the requested accuracy.

Main recent references

Please report any missing information to hprlinfo@oecd-nea.org


  • A. Wallner et al., Novel Method to Study Neutron Capture of 235U and 238U Simultaneously at keV Energies, PRL 112 (2014) 192501, EXFOR 23170
  • J.L. Ullmann, et al., Cross section and g-ray spectra for 238U(n,g) measured with the DANCE detector array at the Los Alamos Neutron Science Center, PRC 89 (2014) 034603, EXFOR 14310
  • H.I. Kim et al., Neutron capture cross section measurements for 238U in the resonance region at GELINA, EPJ A 52 (2016) 170, EXFOR 23302
  • F. Mingrone et al., Neutron capture cross section measurement of 238U at the CERN n_TOF facility in the energy region from 1 eV to 700 keV, PRC 95 (2017) 034604, EXFOR 23234
  • T. Wright et al., Measurement of the 238U(n,g) cross section up to 80 keV with the Total Absorption Calorimeter at the CERN n_TOF facility, PRC 96 (2017) 064601


  • H. Derrien et al., R-Matrix Analysis of 238U High-Resolution Neutron Transmissions and Capture Cross Sections in the Energy Range 0 to 20 keV, NSE 161 (2009) 131
  • R. Dagan et al., Impact of the Doppler Broadened Double Differential Cross Section on Observed Resonance Profiles, ND2013, NDS 118 (2014) 179
  • Kopecky et al., Status of Evaluated Data Files for 238U in the Resonance region, JRC Technical Report, EUR 27504 EN (2015)
  • I. Sirakov et al., Evaluation of cross sections for neutron interactions with 238U in the energy region between 5 keV and 150 keV, EPJ A 53 (2017) 199
  • R. Capote et al., IAEA CIELO Evaluation of Neutron-induced Reactions on 235U and 238U Targets, NDS 148 (2018) 254
  • A.D. Carlson et al., Evaluation of the Neutron Data Standards, NDS 148 (2018) 143


Additional file(s)

  1. International Evaluation Co-operation, Volume 26 - 6.05 MB PDF